Catalytic system which can be used for the stereospecific polymerisation of α-olefins, process for this polymerisation and polymers obtained

Abstract

Catalytic system which can be used for the polymerisation of alpha -olefins comprising: a solid based on complexed titanium trichloride of delta crystalline form; an organoaluminium compound; an organic oxygenated silicon compound; characterised in that the organoaluminium compound is a non-halogenated compound.

We claim: 
     
       1. A catalytic system for the polymerisation of an α-olefin, consisting of: (1) a solid based on complexed titanium trichloride of δ crystalline form, free of magnesium, obtained by reducing titanium tetrachloride or tetraalkoxide with an organoaluminium reducing agent to form a resulting solid, treating said resulting solid with an aliphatic ether electron-donating compound and, either successively or simultaneously, treating said resulting solid with titanium tetrachloride and activating said successively or simultaneously treated resulting solid by bringing it into contact with an activation agent selected from the group consisting of organoaluminium compound and products from the reaction of an organoaluminium compound with a compound chosen from hydroxyaromatic compounds in which the hydroxyl group is sterically blocked,   (2) an organoaluminium compound selected from the non-halogenated organoaluminium compounds of formula   AlR.sub.m Y.sub.3-m        where R represents a hydrocarbon radical, containing from 1 to 18 carbon atoms, Y represents a group selected from the group consisting of --OR 1 , --SR 1  and --NR 1  R 2  in which R 1  and R 2  each represent an identical or different hydrocarbon radical selected from the group consisting of alkyl, aryl, arylalkyl, alkylaryl and cycloalkyl radicals, and m is a number such that 0<m≦3, and   (3) diisobutyldimethoxysilane.   
     
     
       2. The catalytic system according to claim 1, wherein the solid based on titanium trichloride of δ crystalline form is subjected, at any time during its preparation, to a prepolymerisation treatment with an α-olefin. 
     
     
       3. The catalytic system according to claim 1, wherein the non-halogenated organoaluminium compound is selected from the group consisting of trialkyaluminiums and their mixtures. 
     
     
       4. The catalytic system according to claim 1, wherein the molar ratio of the aluminum of the non-halogenated organoaluminium compound to the titanium of the solid based on complexed titanium trichloride of δ crystalline form varies from 1.5 to 20. 
     
     
       5. The catalytic system according to claim 1, wherein that the molar ratio of the aluminum of the non-halogenated organoaluminium compound to the silicon of the organic oxygenated silicon compound varies from 1 to 5. 
     
     
       6. A catalytic system for the polymerisation of an α-olefin, consisting of: (1) a solid based on complexed titanium trichloride of δ crystalline form, free of magnesium, obtained by reducing titanium tetrachloride or tetraalkoxide with an organoaluminium reducing agent to form a resulting solid, treating said resulting solid with an aliphatic ether electron-donating compound and, either successively or simultaneously, treating said resulting solid with titanium tetrachloride and activating said successively or simultaneously treated resulting solid by bringing it into contact with an activation agent selected from the group consisting of organoaluminium compound and products from the reaction of an organoaluminium compound with a compound chosen from hydroxyaromatic compounds in which the hydroxyl group is sterically blocked,   (2) an organoaluminium compound selected from the non-halogenated organoaluminium compounds of formula   AlR.sub.m Y.sub.3-m        where R represents a hydrocarbon radical, containing from 1 to 18 carbon atoms, Y represents a group selected from the group consisting of --OR 1 , --SR 1  and --NR 1  R 2  in which R 1  and R 2  each represent an identical or different hydrocarbon radical selected from the group consisting of alkyl, aryl, arylalkyl, alkylaryl and cycloalkyl radicals, and m is number such that 0<m≦3, and   (3) dicyclopentyldimethoxysilane.   
     
     
       7. The catalytic system according to claim 6, wherein the solid based on titanium trichloride of δ crystalline form is subjected, at any time during its preparation, to a prepolymerisation treatment with an α-olefin. 
     
     
       8. The catalytic system according to claim 6, wherein the non-halogenated organoaluminium compound is selected from the group consisting of trialkyaluminiums and their mixtures. 
     
     
       9. The catalytic system according to claim 6, wherein the molar ratio of the aluminum of the non-halogensted organoaluminium compound to the titanium of the solid based on complexed titanium trichloride of δ crystalline form varies from 1.5 to 20. 
     
     
       10. The catalytic system according to claim 6, wherein that the molar ratio of the aluminum of the non-halogenated organoaluminium compound to the silicon of the organic oxygenated silicon compound varies from 1 to 5.